[test] Added missing variant generator for unittests

Bug: v8:6917
Change-Id: Ic34afb25b74520303cd9ace987fc18e1535e4147
Reviewed-on: https://chromium-review.googlesource.com/879146Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50776}

test/unittests/testcfg.py

@@ -10,6 +10,11 @@ from testrunner.local import testsuite
 from testrunner.objects import testcase
 
 
+class VariantsGenerator(testsuite.VariantsGenerator):
+  def _get_variants(self, test):
+    return self._standard_variant
+
+
 class TestSuite(testsuite.TestSuite):
   def ListTests(self, context):
     shell = os.path.abspath(os.path.join(context.shell_dir, self.name))
@@ -50,6 +55,9 @@ class TestSuite(testsuite.TestSuite):
   def _test_class(self):
     return TestCase
 
+  def _variants_gen_class(self):
+    return VariantsGenerator
+
   def _LegacyVariantsGeneratorFactory(self):
     return testsuite.StandardLegacyVariantsGenerator